New environmentally friendly pigments based on Ln2Zr2-XFexO7-x/2

Abstract

In this study, the application of materials with A2B2O7 stoichiometry is addressed. Two compositions with different lanthanides ion in A position, Gd2Zr2O7 and Ce2Zr2O7, and doped with the same cation (Fe(III)) in B position, have been chosen for this work. The influence of the lanthanide and the iron ions on the structural and optical properties, in particular the colour of this material has been analysed. In the same way, two synthesis methods, coprecipitation and hydrothermal, were compared to analyse which one had a greater effect on phase stabilization and the final coloration. Both the trivalent cation at A position and the synthesis route, played a key role in the final product characteristics. The structure of the solids was analysed by X-ray diffraction (XRD) and UV-Vis spectroscopy was used to study the optical properties of these pigments. The pigments with composition based on Gd2Zr2-xFexO7-x/2 presented single phase of defect fluorite, in contrast, powders with formula Ce2Zr2-xFexO7-x/2 could not be synthesized with single phase. Besides, powders obtained by solvothermal method presented single phase and the limit of solid solution was x=0,25, for the Gd2Zr2-xFexO7-x/2 compositions. Finally, the colouring of the pigments, according to CIE L*a*b chromatic coordinates, was better in the case of solvothermal synthesis for Gd2Zr2-xFexO7-x/2 samples, as the reddish coordinate presented a slightly higher value.